The present invention relates to magnetic tape drives for the storage of digital data and more particularly, to a high speed buffered tape drive having conventional sized reels which can be mounted in a standard rack configuration.
Magnetic tape units for storing digital data typically accelerate tape from a stop to a high speed very rapidly on demand of a processing unit. In order to achieve this, the main mass of the tape must be decoupled from the tape in the immediate vicinity of the capstan and the read/write head.
Typically, vacuum columns have been used to decouple the inertia of tape on the machine and file reels from the capstan. U.S. Pat. No. 4,331,306--Epina, et al shows a magnetic tape drive with vacuum column decoupling which can be mounted in a standard rack configuration.
While vacuum columns are suitable for tape drives in many applications, there are other applications, particularly for small rack-mounted tape drives, in which vacuum columns have significant disadvantages.
Swing arms, or tension arms, have previously been used instead of vacuum columns for buffering the tape drive capstan from the inertia of tape on the reels. U.S. Pat. No. 4,243,186--Peter, et al is an example. This patent discloses a tape drive with a single swing arm and a pneumatic path for automatically threading the tape past the swing arm. Automatic threading is relatively straightforward in such a tape drive, but accomplishing automatic threading in a tape drive with two decoupling double roller swing arms, one arm for each reel, is much more difficult.
It is an object of the present invention to provide a compact digital magnetic tape drive using swing arms to decouple the tape to obtain the advantages of reduced cost and reduced noise when compared to vacuum column buffered tape drives.
It is another object to provide a tape buffering system having a large amount of tape to be buffered in a minimum amount of space and with the ability to accelerate the tape to final velocity rapidly.
It is another object of the present invention to provide automatic threading in a magnetic tape drive in which two swing arms decouple the inertia of the tape on the reels from the capstan and in which tape is tensioned during running by swing arms having two rollers which draw two loops of tape across a fixed roller.